Comments by "Keit Hammleter" (@keithammleter3824) on "Overcoming The Rotary Engine’s Biggest Flaw" video.

The biggest flaw of the Wankel engine is not the apex seals - Mazda solved that quite adequately. The biggest flaw is the completely stupid combustion chamber shape - giving low fuel efficiency.
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@mKarsten No. The Mazda seals last quite adequately. Mazda forums indicate life exceeding 100,000 km even in early RX-7's provided they are not hotted up with turbos etc. Mazda has improved the seals further order the years and 200,000 km is now the norm. In principle, the seal issue, which is a durability issue, is solvable, given sufficient ingenuity. But there is NOTHING that can be done about the combustion chamber shape, so the engine is inherently inefficient. Ideally, you want to minimize the combustion surface area for a given combustion volume, as that minimises the loss of combustion heat via the surrounding metal into the coolant. The best possible shape from this point of view is a sphere. You cannot of course have a perfect sphere as the shape must change in order to have compression and expansion. But a hemi head on a piston engine come the closest, closely followed by bowl-in-piston designs. The combustion chamber in a Wankel engine inherently has to be long and thin, giving a very much worse volume to area ratio.
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@WilhelmKarsten You sir are not only confused and misinformed, as a check of forums devoted to Madza rotaries will show, you have missed my point that there are two issues:- durability issues - an engine may perform well but have a short life; and fundamental design issues - fundamental principles may prevent an engine from operating efficiently. The first kind are amenable to sufficient ingenuity, the second are not. Mazda or someone else may further improve the life of the apex seals, which are already adequate, but there is NOTHING they can do about the high fuel consumption.
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@WilhelmKarsten : As would be clear from various posts I have made on different YouTube videos, and as would be revealed with a bit of elementary googling, I am a professional engineer with years of engine experience, principally for a certain American manufacturer whose corporate colours are black and yellow. A Wankel engine would be no good for aircraft, regardless of any apex seal issue, due to its high fuel consumption - in aircraft, fuel economy is much more critical that it is for cars. So I very much doubt that Mazda, the only Wankel manufacturer since NSU dropped out decades ago, ever bothered to seek airworthiness certification. It is not their market anyway. The Wankel does make some (limitted) sense in a sports car due to its smoothness and ability to rev high. Which raises another point - aircraft propellors work most efficiently at around 2300 RPM or less, which matches piston engines pretty good, but not the high revving Wankel. A question for you kiddo - what are your relevant qualifications or experience? 15 minutes watching YouTube videos? Can you provide evidence of your claim? You can verify what I said about combustion chamber shape by consulting any decent engine engineering text book. You can verify Mazda apex seal life by googling. Can you provide evidence of your claim?
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@DoktorBayerischeMotorenWerke You have things backwards and also have some misconceptions. High swirl, because of the reduction and even out of temperature within the combustion space, reduces the tendency to pre-ignite and allow you to increase the compression ratio in gasoline engines - which may increase power output and partly, but not wholly, compensate for the increase heat conduction. high swirl means high heat loss as it thins the boundary ("Carrier") layer - the layer of substantially non-moving gas adhering to surfaces. It is why combustion can reach white heat yet the head doesn't melt even if aluminium. Non-moving gas is a heat insulator. In diesel engines pre-ignition cannot occur, and so bowl-in-piston designs are still dominant. As I said earlier, bowl-in-piston design is an equally performing alternative to hemi-head. But it transfers more heat to the piston instead of the head, so it has only been used in small car engines (eg Ford Cortina) and in turbo engines where the piston needs to spray oil cooled anyway - as in modern diesels. Wedge head designs, along with bathtubs, were a feature of 1950's engines as they similarly reduce pre-ignition and make the engine non--critical in tuning. A pent-roof is essentially a hemi. The modern use of 4 valves as large as possible with only one or 2 camshafts forces the top surfaces to be somewhat flat, and this has led to marketing people calling it pent-roof. The large area devoted to valves improves breathing and thus power output at high RPM but does nothing for efficiency. It is all very well to keep saying apex seals are prone to failure, however it is a fact that Mazda have achieved acceptable seal life.
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